It's my mistake. change the " to ', then OK. Now the follow code can be run :
#!/usr/bin/perl

#
# PROCEDURE `TEST_COUNT_PLUS`
#
# CREATE DEFINER=`root`@`localhost` PROCEDURE `TEST_COUNT_PLUS`(INOUT 
+NUMBER1 INTEGER)
# BEGIN
   # DECLARE NUMBER2 INTEGER
      # DEFAULT (SELECT COUNT(*) FROM PLAYERS);
   # SET NUMBER1 = NUMBER2 + NUMBER1;
# END$$

use strict;
use DBI;

my @hit_count;
my $dbh = DBI->connect('dbi:mysql:tennis','BOOKSQL','BOOKSQLPW') or di
+e "Connection Error: $DBI::errstr\n"; 
$dbh->do('set @hit_count=10'); # change " to ', disable interpreter.

my $sql = 'call TEST_COUNT_PLUS(@hit_count)';
my $sth = $dbh->prepare($sql);
$sth->execute || die $DBI::errstr;
$sth->finish; 

# Now get the output variable
my @result = $dbh->selectrow_array('SELECT @hit_count') || die $DBI::e
+rrstr;
print "result=", $result[0], "\n";

$dbh->disconnect;

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In reply to Re^5: Calling MySQL stored procedures with in and out parameters by morning_leaf
in thread Calling MySQL stored procedures with in and out parameters by Benedict White

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